The present invention relates to an igniter for controlling a primary current to be turned on or off, which is used with an ignition device for internal combustion engine, and more particularly to an ignition device for internal combustion engine in which an igniter and an ignition coil are integrated within an ignition device case.
Conventionally, there is proposed an ignition device for internal combustion engine in which an igniter and an ignition coil are equipped within the same ignition device case. Particularly in recent years, the ignition device arranged for each ignition plug is spread. FIG. 5 shows the structure of an igniter for use with this ignition device, and FIG. 6 show a method of mounting the igniter on the ignition coil of the ignition device for internal combustion engine. As previously described, the ignition coil and the igniter are indispensable for each other and employed as a set in the ignition device for internal combustion engine.
In FIGS. 5 and 6, the ignition device has a primary coil and a secondary coil buried in a plug hole provided in an engine main body, not shown, in which an igniter 10 is disposed directly above the coil portion and outside the plug hole, these being accommodated within an ignition device case. As shown in FIG. 5, the igniter 10 is connected to a connector 1 having an external connection terminal 2 for supplying the power from a battery or the like, and an igniter metal terminal 9 connected to the external connection terminal 2. A cover 11 made of an elastic material such as resin is put on the igniter 10, and a filling epoxy resin is filled in the entity of the igniter 10 and cured to have the finished product.
As above described, when the igniter 10 is mounted on the ignition coil 13 as shown in FIG. 6, there is a need for preparing the connector 1 separately as the external connection terminal of the igniter 10, as shown in FIG. 5.
When the igniter 10 is mounted on the ignition coil 13, first of all, the igniter 10 is fitted into the connector 1. Then, the igniter metal terminal 9 provided on the side face of the igniter 10 and the external connection terminal 2 provided in the connector 1 are joined by welding or the like.
In this manner, an igniter connector ASSY 12 having the connector 1 fitted is attached to the ignition coil 13. Thereafter, the upper part of the ignition coil 13 having the igniter 10 mounted is filled and sealed with the filling epoxy resin 14, whereby the igniter 10 is fixed.
Generally, in the prior art, the igniter 10 of FIG. 5 has the components packaged internally on one face or both faces of a single plane or a single layer of the substrate, whereby the igniter 10 has a large current portion and a small current portion of the circuit placed proximately on the internal wiring substrate.
However, the igniter 10 has the following problems. A first problem is that the connection with the external connection terminal 2 must be made using the connector 1 that is prepared as a separate part, and before the igniter 10 itself is placed in the ignition coil 13, the electrical or mechanical connection between the igniter 10 and the connector 1 by welding or the like is required, increasing in the number of parts, degrading the operability of welding, or increasing the number of steps needed for welding. More specifically, with the above constitution, a number of bonding points are required corresponding to the number of external terminals, and if the number of bonding or welding points is increased, there occurs a problem with non-contactness at the connection, with the reliability lower in proportion to an increase in the number of contact portions.
A second problem is that a mounting portion of the igniter 10 in the ignition coil 13 is filled and sealed with the filling epoxy resin 14 to fix the igniter 10 joined with the connector 1, but the igniter 10 itself is of the structure that is only molded with the molding resin 7, whereby the cover 11 is needed as a separate part to relieve a stress due to thermal expansion or contraction of the filling epoxy resin 14. In this respect, there is the problem with the increased number of parts, poor operability, the increased number of steps, and the lower reliability.
Further, a third problem is that when all the components are arranged on a single plane of the internal wiring substrate or lead frame to give the added value to the igniter, it is necessary to take a large space for the internal wiring substrate, and the igniter 10 is limited in saving the space. Further, when the internal wiring substrate is employed for packaging the components, the components are arranged on the single or double faces of the internal wiring substrate, whereby the large current portion and the small current portion are placed proximately in the circuit of the internal wiring substrate, causing a current produced during the operation of the igniter 10 to affect adjacent conductive patterns, and causing the noise of the igniter 10 due to an interference of electromagnetic induction, resulting in an adverse influence on the primary current shut-off control. Moreover, there remains the unsolved problem that when the igniter 10 is driven, heat produced from the internal packaged components will easily affect the components on the single plane.